Rotary hydraulic machines

ABSTRACT

A radial piston pump has two rows of radial bores and two associated movable cam rings. The cam rings are constrained to move in unison by arms which are secured to a hollow shaft extending parallel to the axis of the pump rotor. Within the shaft is a passage by means of which the high pressure ports associated with respective rows of bores are interconnected.

United States Patent 91 [111 3,786,726 Freeman Jan. 22, 1974 I54] ROTARY HYDRAULIC MACHINES 2,949,08l 8/I96O Dcschnmpfl HR/30 9 I751 Inventor: Frank George Freeman, solihuu. i'fiifi'fi? i531; 212212,, 9523i Warwickshire, England [73] Asslgnee; 22 g szt Lmmed Primary Examiner-William L. Freeh g g Assistant Examiner-Gregory LaPointe [22] Filed: Oct. 19, 1971 Attorney, Agent, or Firm'Holman & Stern [21] Appl. N0.: 190,632

[30] Foreign Application Priority Data [57] ABSTRACT OCt. 21, Great A radial piston pump has two rows of radial bores and two associated movable cam rings. The cam rings are [52] US. Cl. 91/492, 91/497 constrained to move in unison by arms which are 1. cured to a hollow shaft extending parallel to the axis [58] Field of Search ..9-1[492, 497; 92/ 12.1; f the pump town within the h f is a passage by v 417/221 means of which the high pressure ports associated with respective rows of bores are interconnected. [56] References Cited vUNITED STATES PATENTS 10 Claims, 4 Drawing Figures 2,895,426 7/1959 Orshansky 91/492 ROTARY HYDRAULIC MACHINES This invention relates to rotary hydraulic machines, such as pumps and motors and has as an object to provide such a machine in a convenient form.

According to the invention a rotary hydraulic machine comprises a casing, a rotor mounted within the casing, an axially spaced pair of rows of radial bores in the rotor, a plurality of pistons slidable in the bores, a pair of cam rings surrounding the rotor within the casing, with which rings the rows of pistons are respectively engageable, a pair of passages in the casing with which the bores in the respective rows successively, in use, communicate, actuating means operable to move the rings to a desired eccentricity with respect to the rotor, a linkage operatively connecting the rings, the said linkage including a shaft within the casing, and a conduit within the shaft interconnecting the said passages.

A hydraulic pump according to the invention will now be described by way of example and with reference to the accompanying drawings, in which:

FIG. 1 is a longitudinal section through a pump,

FIGS. 2 and 3 are sections on the corresponding lines in FIG. 1, and

FIG. 4 is a diagrammatic representation of part of the pump.

The pump has a casing 10 formed in two parts 11, 12. .lournalled in bearings 13 in the casing 10 is a rotor 14 formed with two rows l5, 16 of stepped radial bores 17. Piston assemblies 18 are slidable in the bores 17 and include slipper members 19. Surrounding the rotor 14 and pivotally mounted in the casing 10 on respective pins 20, 21 are a pair of cam rings 22, 23 against the inner surfaces of which the piston assemblies 18 of the rows 15, 16 are respectively engageable.

An axial bore 40 extends through the rotor 14. The piston assemblies 18 includes stems 41 which extend into the bore 40 and engage thimbles 42 which serve to maintain the piston assemblies 40 closely adjacent to the cam rings 22, 23 and thus prevent the slipper members 19 from becoming separated. The thimbles 42 are maintained in the correct axial spacing within the bore 40 bydumb-bellshaped members 53.

Each of the bores 17 has an associated port 24 which opens onto an adjacent end face of the rotor 14. A pair of generally semicircular port plates 25, 26 abut the ends of the rotor 14. Each of the plates 25, 26 includes a single kidney. port 54, as shown in FIG. 4, which extends round the circumference of the plate and which is aligned with the ports 24 in the rotor 14. The kidney ports 54 in the plates 25, 26 respectively communicate with passages 27, 28 in the casing 10, and the port in the plate 26 communicates with an outlet 29 for the pump. When the ports 24 in the rotor 14 are not aligned with the plates 25, 26 they communicate, via the interior of the casing 10, with an inlet 30 for the pump. A bush 31 lies within the wall of the casing 10 parallel to the axis of the rotor 14 and has a bore 32 by means of which passages 27, 28 intercommunieate.

A piston 33 engages the cam ring 23 and is movable radially in response to the pressure in an associated cylinder 34 in the casing part 11 to increase the eccentricity of the cam ring 23 with respect to the rotor 14. A piston 35, of considerably smaller diameter than piston 33, is similarly movable in a cylinder 36 to decrease .the eccentricity of cam ring 22 with respect to the rotor 14.

Rotatable on the bush 31 is a hollow shaft 37 from opposite sides of which extend a pair of integral levers 38, 39 which respectively engage the cam rings 22, 23 ensuring that the eccentricity of the cam rings with respect to the rotor 14' is always equal.

Cylinder 36 communicates with outlet 29 via a stepped bore 43 (FIG. 3) in the casing 10. Cylinder 34 also communicates, via a flow restrictor 49 and a port 50 with the bore 43. The ends 44, 45 of bore 43 communicate with pump inlet 30. Slidable in bore 43 is a piston member 46 having an associated spool valve control member 47 by means of which cylinder 34 may be made to communicate, via bore 43, either with outlet 29, or inlet 30 or with both inlet 30 and outlet 29. In the latter case member 47 co-operates with port 50 to provide a potentiometer arrangement whereby the pressure in cylinder 34 is intermediate the pressures at the inlet 30 and outlet 29. Cylinder 34 also communicates via a normally-closed solenoid valve 48 with the inlet 30. Piston member 46 is responsive to the difference between the pressures at the inlet 30 and outlet 29 and is, moreover, biased by a spring 51 in a direction so that, when the pressure difference is below a predetermined amount, cylinder 34 is in communication with outlet 29.

In use, the pump operates in a known manner to take up fluid at inlet 30 and discharge it under pressure from outlet 29, the volume of fluid discharged per revolution of the rotor 14 being dependent on the eccentricity of the cam rings 22, 23 with respect to the rotor 14. Below a predetermined level of pressure at the outlet 29, pressure in cylinders 34, 36 is equal, the difference in cylinder diameters ensuring that the cam rings are moved to positions of maximum eccentricity to provide maxi- .mum pump displacement. At outlet pressures above this predetermined level piston 46 is moved to the left, as seen in FIG. 3, to provide a reduced pressure in cylinder 34. The pump stroke is thereupon reduced by piston 35, reducing the pressure at outlet 29 to a level at which equilibrium again exists. Operation of solenoid valve 48 destrokes the pump immediately by releasing the pressure in cylinder 34. Restrictor 49 limits loss of 'high pressure fluidwhen valve 48 is operated.

The use of shaft 31 as a passage to interconnect the high pressure ports of both halves of the pump, allows the pump to be made as a compact assembly with a minimum of external pipe connections.

It will be understood that an arrangement as above described is equally applicable to a hydraulic motor.

I claim:

l. A rotary hydraulic machine comprising a casing, a rotor mounted within the casing, an axially spaced pair of rows of radial bores in the rotor, a plurality of pistons slidable in the bores, a pair of cam rings surrounding the rotor within the casing, with which rings the rows of pistons are respectively engageable, a pair of passages in the casing with which the bores in the respective rows successively, in use, communicate, actuating means operable to move the rings to a desired eccentricity with respect to the rotor, a linkage operatively connecting the rings, said linkage including a hollow bush within the casing, a shaft journalled on said bush, and a conduit within the bush interconnecting said passages.

2. A machine as claimed in claim 1 in which said cam rings are pivotally mounted in said casing.

3. A machine as claimed in claim 1 in which said actuating means comprises a first piston engageable with one of said rings and subjected to the pressure at a high pressure port of the machine, a second piston of larger diameter than said first piston, said second piston being engageable with the other of said rings and being subjected to a pressure intermediate the pressures at said high pressure port and at a low pressure port of the machine, and means for varying said intermediate pressure.

4. A machine as claimed in claim 3 in which movement of said first piston in response to said pressure at the high pressure port increases the eccentricity of said rings with respect to the rotor and movement of said second piston in response to an increase in said intermediate pressure reduces the eccentricity of the rings.

5. A machine as claimed in claim 4 in which said means for varying the intermediate pressure comprises a flow control valve via which said second piston can communicate with the high and low pressure ports respectively.

6. A machine as claimed in claim 5 in which said flow restriction means comprises a spool valve.

7. A machine as claimed in claim 6 which includes servo-actuating means responsive to an increase in the difference between the pressures at said high and low pressure ports to move the spool valve in a direction to increase said intermediate pressure.

8. A machine as claimed in claim 1 in which said cam rings are movable in opposite directions relative to the thimbles. 

1. A rotary hydraulic machine comprising a casing, a rotor mounted within the casing, an axially spaced pair of rows of radial bores in the rotor, a plurality of pistons slidable in the bores, a pair of cam rings surrounding the rotor within the casing, with which rings the rows of pistons are respectively engageable, a pair of passages in the casing with which the bores in the respective rows successively, in use, communicate, actuating means operable to move the rings to a desired eccentricity with respect to the rotor, a linkage operatively connecting the rings, said linkage including a hollow bush within the casing, a shaft journalled on said bush, and a conduit within the bush interconnecting said passages.
 2. A machine as claimed in claim 1 in which said cam rings are pivotally mounted in said casing.
 3. A machine as claimed in claim 1 in which said actuating means comprises a first piston engageable with one of said rings and subjected to the pressure at a high pressure port of the machine, a second piston of larger diameter than said first piston, said second piston being engaGeable with the other of said rings and being subjected to a pressure intermediate the pressures at said high pressure port and at a low pressure port of the machine, and means for varying said intermediate pressure.
 4. A machine as claimed in claim 3 in which movement of said first piston in response to said pressure at the high pressure port increases the eccentricity of said rings with respect to the rotor and movement of said second piston in response to an increase in said intermediate pressure reduces the eccentricity of the rings.
 5. A machine as claimed in claim 4 in which said means for varying the intermediate pressure comprises a flow control valve via which said second piston can communicate with the high and low pressure ports respectively.
 6. A machine as claimed in claim 5 in which said flow restriction means comprises a spool valve.
 7. A machine as claimed in claim 6 which includes servo-actuating means responsive to an increase in the difference between the pressures at said high and low pressure ports to move the spool valve in a direction to increase said intermediate pressure.
 8. A machine as claimed in claim 1 in which said cam rings are movable in opposite directions relative to the rotor to increase said eccentricity.
 9. A machine as claimed in claim 8 in which the said linkage comprises a pair of levers secured to said shaft and extending from opposite sides thereof, said levers engaging respective ones of said cam rings.
 10. A machine as claimed in claim 1 which includes an axial bore in said rotor, a pair of thimbles within said bore at axial locations therein corresponding to the axial positions of said rows of radial bores and stems on said pistons extending into said axial bore to engage the thimbles. 